This invention relates generally to methods for fracturing a formation communicating with a well, such as a hydrocarbon-bearing formation intersected by an oil or gas production well.
There are various uses for fractures created in subterranean formations. In the oil and gas industry, for example, fractures may be formed in a hydrocarbon-bearing formation to facilitate recovery of oil or gas through a well communicating with the formation.
Fractures can be formed by pumping a fracturing fluid into a well and against a selected surface of a formation intersected by the well. Pumping occurs such that a sufficient hydraulic pressure is applied against the formation to break or separate the earthen material to initiate a fracture in the formation.
A fracture typically has a narrow opening that extends laterally from the well. To prevent such opening from closing too much when the fracturing fluid pressure is relieved, the fracturing fluid typically carries a granular or particulate material, referred to as “proppant,” into the opening of the fracture. This proppant remains in the fracture after the fracturing process is finished. Ideally, the proppant in the fracture holds the separated earthen walls of the formation apart to keep the fracture open and provides flow paths through which hydrocarbons from the formation can flow at increased rates relative to flow rates through the unfractured formation.
Such a fracturing process is intended to stimulate (that is, enhance) hydrocarbon production from the fractured formation. Unfortunately, this does not always happen because the fracturing process can damage rather than help the formation.
One type of such damage is referred to as a screen-out or sand-out condition. In this condition, the proppant clogs the fracture such that hydrocarbon flow from the formation is diminished rather than enhanced. As another example, fracturing can occur in an undesired manner, such as with a fracture extending vertically into an adjacent water-filled zone. Because of this, there is a need for a method for fracturing a formation that provides for real-time control of the fracturing process.